help: for command

hi,
please can someone help me with the for command.
let's take a really stupid but simple example where i wish to cat all the
files in a directory. note that i don't ever do this this is just an
example of where the for command doesn't work for me:
for i in *.txt; cat "checked this file" >>i; done
in such an example i get a file called i that contains the same line lots of
times.
under dos the following would work:
for %1 in (*.txt) do type "checked this file" >>%1
so any tips where i'm going wrong under linux?
thanks, saqib